Extraction and recovery of methylene blue from industrial wastewater using benzoic acid as an extractant

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Journal of Hazardous Materials 163 (2009) 363–369

Contents lists available at ScienceDirect

Journal of Hazardous Materials

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xtraction and recovery of methylene blue from industrial wastewater usingenzoic acid as an extractant

. Muthuraman, Tjoon Tow Teng ∗, Cheu Peng Leh, I. Norlichool of Industrial Technology, Universiti Sains Malaysia, Penang 11800, Malaysia

r t i c l e i n f o

rticle history:eceived 13 February 2008eceived in revised form 25 June 2008ccepted 26 June 2008vailable online 9 July 2008

a b s t r a c t

Liquid–liquid extraction (LLE) of methylene blue (MB) from industrial wastewater using benzoic acid(extractant) in xylene has been studied at 27 ◦C. The extraction of the dye increased with increasingextractant concentration. The extraction abilities have been studied on benzoic acid concentration inthe range of 0.36–5.8 × 10−2 M. The distribution ratio of the dye is reasonably high (D = 49.5) even in thepresence of inorganic salts. Irrespective of the concentration of dye, extraction under optimal conditions

eywords:iquid–liquid extractionethylene blue

xtractantiluenttripping agent

was 90–99% after 15 min of phase separation. The extracted dye in the organic phase can be back extractedinto sulphuric acid solution. The resultant recovered organic phase can be reused in succeeding extractionof dye with the yield ranging from 99 to 87% after 15 times reused, depending on the concentration ofthe initial feed solution. Experimental parameters examined were benzoic acid concentration, effect ofdiluent, effect of pH, effect of initial dye concentration, effect of equilibration time, various strippingagents, aqueous to organic phase ratio in extraction, organic to aqueous phase ratio in stripping andreusability of solvent.

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. Introduction

Among different pollutants of aquatic ecosystem dyes are a largend important group of chemicals. They are widely used in indus-ries such as textile, paper, rubber, plastic, cosmetic, etc., to colourhe products. These dyes are invariably left in the industrial wastend consequently discharged mostly to surface water resources.yes even in low concentration are visually detected and affect thequatic life and food web. These coloured compounds are not onlyesthetically displeasing but also inhibiting sunlight into streamsnd affecting photosynthetic reaction [1]. It is estimated that morehan 100,000 commercially available dyes with over 7 × 105 tons ofyestuff are produced annually [2]. Methylene blue (MB) is one ofhe most commonly used substances for dyeing cotton, wood andilk. Though MB is not strongly hazardous, it can cause some harm-ul effects where acute exposure to MB will cause increased heartate, vomiting, shock, cyanosis, jaundice, and quadriplegia and tis-ue necrosis in humans [3]. The advantages and disadvantages of

ome methods of dye removal from wastewater are given in Table 14].

Removal of MB by carbon derived from peach stones by H3PO4ctivation was studied [5]. Adsorption of MB by algal biomass

∗ Corresponding author. Tel.: +60 4 6532215; fax: +60 4 6573678.E-mail addresses: [email protected], [email protected] (T.T. Teng).

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304-3894/$ – see front matter © 2008 Elsevier B.V. All rights reserved.oi:10.1016/j.jhazmat.2008.06.122

© 2008 Elsevier B.V. All rights reserved.

ased materials was also reported [6]. Kavitha and Namasivayam7] also used coir pith activated carbon. The adsorption capacityas found to be 5.87 mg/g by Langmuir isotherm for the particle

ize of 250–500 �m. In these cases disposal of spent activated car-on is a problem. Micellar enhanced ultra filtration (MEUF) is oneossible method to remove organic dyes from water. Even thoughEUF method is not yet applied on an industrial scale, many studies

ave shown that it is a suitable method for the retention of metalons [8,9], anions [10], and organic pollutants [11,12]. Separation of

B from aqueous solution by micellar enhanced ultra filtration waslso reported [13].

Electrochemical degradation of MB was studied by Panizza etl. [14]. Photo catalytic degradation of MB was also investigated15,16]. Removal and recovery of dye stuffs (DSs) using ion exchange

ethod was proposed by MonaNaim and Yehia [17]. Electrochemi-al oxidation of dye wastewater was studied by various researchers18,19]. Sundrarajan et al. [20] reported that ozonation is efficient inecolorization of exhausted dye bath effluent containing conven-ional reactive dyes. Ozone treatment was used on acid red 18, acidrange 7, acid orange 10 and acid red 73 by Muthukumar et al. [21].or all the dyes two successive recycling processes were carried out.

zonation method does not remove total dissolved solids (TDS), but

t reduces chemical oxygen demand (COD) of the effluent.Membrane separation process plays an increasing role in the

eduction and/or recovery of DSs. Fouling of membrane is a prob-em in this case [22]. Removal of anionic and cationic organic dyes

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364 G. Muthuraman et al. / Journal of Hazardous Materials 163 (2009) 363–369

Table 1Advantages and disadvantages of the current methods of dye removal from industrial effluent [4]

Physical/chemical methods Advantages Disadvantages

Fenton’s reagent Effective decolourization of both soluble and insoluble dyes Sludge generation due to Fe2+ usedOzonation Applied in gaseous state no alternative of volume Short half life (20 min) of ozonePhotochemical No sludge production Formation of by productsNaOCl Initiate and accelerates azo bond cleavage Release of aromatic amines and adsorption of organic halidesElectrochemical destruction Breakdown compounds are non hazards High costActivated carbon Good adsorbent due to cellular structure Very expensive and disposal of spentPeat Good adsorbent due to cellular structure Specific surface areas of adsorbent are lower than activated carbonWSI

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sstransferred into a separating funnel. The aqueous strippant wastaken for dye concentration measurements. All the experimentswere run in duplicate and analytical parameters were performedin triplicate for each run. Confidence limit of 95% was taken forreliable results.

ood chips Good sorption capacity for acid dyesilica gel Effective removal for basic dyeson exchange Regeneration, no adsorbent loss

rom water by liquid–liquid extraction (LLE) using reverse micellesas proposed by Pandit and Basu [23]. Removal of methyl orange

nd methylene blue dyes from water using colloidal gas aphronsCGA) was reported by Basu and Malpani [24]. Roy et al. [25] stud-ed the separation of organic dyes such as methyl orange, methylenelue, cibacrome 4G, cibacrome 6B from wastewater using CGA.exa tetramethyl ammonium bromide and sodium dodecyl ben-ene sulphonate were used as surfactants for the generation ofGA.

Aqueous bibasic system (ABS) consists of two immiscible phasesormed when certain water soluble polymers are mixed with onenother or with certain inorganic salts in specific concentration26]. ABS composing of dodecyl trimethyl ammonium hydroxidend sodium dodecyl sulphates was reported to be able to extractethyl orange and porphyry dyes [27].Liquid–liquid extraction method is used for the purification

nrichment separation and analysis of various compounds in mix-ures. It is based on the principle that a solute can distribute itself incertain ratio between immiscible solvents. Therefore, the selec-

ion of both a diluent and an extractant determines equilibriumor a given system and the efficiency of extraction process dependsn its mass transfer rate [28]. The advantage of solvent extractionncludes high through put, ease of automatic operation and of scalep and high purification [29]. The main factors affecting LLE pro-ess are, organic to aqueous phase ratio, salt concentration, naturef solvent, salting effect and some of the interference mechanisms.

In the present study, the efficiency of liquid–liquid extractionf a cationic dye namely, methylene blue using benzoic acid pre-ared in xylene as extractant was studied. The dye extraction andtripping extracted dye were investigated and operating conditionsere optimized. Further recovery of dye and stripping reagentsere also studied.

. Experimental

.1. Materials

Benzoic acid, xylene, methylene blue, sulphuric acid, sodiumydroxide, sodium chloride, nitric acid and hydrochloric acid, werebtained from Merck. All chemicals used in this study were of ARrade.

A UV–visible spectrophotometer (Spekol 1200, Analytical Jena,ermany) was used to measure the absorbance of the dye and tostablish its �max and its concentration. pH of an aqueous solutionas measured by a pH meter (WTW, Germany). For agitation of

olutions a mechanical stirrer was used (IKD-KS 50, Germany).Benzoic acid was used as extractant and dissolved in xylene. The

ye solution was prepared in distilled water. Sulphuric acid wassed as stripping agent and sodium hydroxide was used to adjustH.

Ff

Requires long retention timePrevent commercial applicationNot effective all types of dyes

.2. Procedure

.2.1. Liquid–liquid extraction of dyeThe organic solvent [(benzoic acid + xylene) (Vo mL)] used for

xtraction was added to the prepared aqueous dye solution (Va mL)n a glass-stoppered bottle and the glass-stoppered bottle washaken for known time in a shaker at 100 rpm. The solution washen transferred into a separating funnel. Sample of aqueous solu-ion at the bottom of the separating funnel was taken for absorbance

easurement of dye. The wavelength of maximum absorption�max) for methylene blue was 650 nm. The experimental setups shown in Fig. 1. The distribution ratio (D) and percentage ofxtraction (E) were calculated as per the following equations

= [dye]org

[dye]aq(1)

= 100 × [dye]aq0 − [dye]aq

[dye]aq0(2)

here [dye]org is the dye concentration in the organic phase (mg/L),dye]aq0 is the initial dye concentration of aqueous phase (mg/L),dye]aq is the dye concentration of aqueous phase after extractionmg/L).

In stripping, the loaded extractant (Vo mL) and the aqueoustrippant (acid solution) were added together into a glass-toppered bottle and shaken at 100 rpm. The content was then

ig. 1. Schematic experimental setup for liquid–liquid extraction for removal of dyerom aqueous solution.

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G. Muthuraman et al. / Journal of Hazardous Materials 163 (2009) 363–369 365

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Table 2Effect of extractant concentration

Extractantconcentration (M × 102)

Percentage of dyeextraction

Distributionratio (D)

0 0 00.36 55.3 27.60.72 62.3 31.11.45 85.7 42.825

E

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(3)

ig. 2. Effect of pH in the feed solution (experimental conditions: volume ofource phase = 25 mL, volume of organic phase = 25 mL, extractant concentration.9 × 10−2 M, equilibration time = 10 min).

The extraction and stripping processes were repeated on aque-us dye solutions in which inorganic salts were added to study theffect of the presence of these salts.

. Results and discussion

.1. Effect of pH of source phase

The effect of pH of the source phase on the efficiency of dyextraction is shown in Fig. 2. Aqueous solutions of different con-entrations were maintained in the range of pH 7–13 to study dyextraction efficiency. Maximum extraction efficiency was noticed

s follows: 99% for 50 mg/L, 96% for 100 mg/L, 95% for 200 mg/L,4% for 300 mg/L and 90% for 500 mg/L, respectively. It can be seenhat percentage of dye extraction increased with increasing pH ofqueous solution. The results reveal that the maximum extractionf dye had occurred in the pH range 10–13. For further studies, itas decided to maintain the extraction at pH 12 ± 0.1.

.2. Effect of extractant concentration

The effect of benzoic acid concentration on distribution ratio

D) of the dye was next investigated in the concentration range of.36 × 10−2 to 5.8 × 10−2 M. Table 2 shows that the efficiency of dyextraction increased with increasing benzoic acid concentration.aximum extraction of 99% occurred at benzoic acid (50 mg/L) con-

entration of 2.9 × 10−2 M. Further increase (beyond 2.9 × 10−2 M)

Fa2

.91 99.0 49.5

.81 99.0 49.5

xtraction phase ratio 1:1.

n extractant concentration did not show considerable effect onxtraction efficiency. It is interesting to note that in the absencef benzoic acid no extraction of dye occurred in the organic phase.his confirms that benzoic acid is effective in extracting cationicye. Hence in the succeeding test the extractant benzoic acid con-entration was fixed at 2.9 × 10−2 M.

To determine the nature of the extracted dye, dye solutions ofifferent concentrations were extracted by fixed concentration ofenzoic acid (2.9 × 10−2 M). The distribution ratio (D) of dye wasalculated at fixed concentration of benzoic acid. The plot of logxtracted dye versus log feed concentration (mg L−1) (Fig. 3) givesstraight line with a slope value of 1.0356 indicating that dye to

xtractant concentration ratio was best at 1:1 and suggesting for-ation of 1:1 complex. It can then be assumed that 1 mol of benzoic

cid can best extract 1 mol of cationic dye [22]. The reaction forxtracting the dye is as follows.

ig. 3. Distribution ratio (experimental conditions: volume of source phase = 25 mLt pH 12 ± 0.1, volume of organic phase = 25 mL, extractant concentration.9 × 10−2 M, equilibration time = 10 min).

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366 G. Muthuraman et al. / Journal of Hazardous Materials 163 (2009) 363–369

Table 3Effect of diluents on dye extraction efficiency

Diluents Percentage of dye extraction

Hexane 5.0Methylene chloride 70.1TXB

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Fig. 5. Effect of equilibration time (experimental conditions: volume of sourcephase = 25 mL at pH 12 ± 0.1, volume of organic phase = 25 mL, extractant concen-tration 2.9 × 10−2 M).

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1e

oluene 95.0ylene 99.0enzene 75.3

xtraction phase ratio 1:1.

.3. Effect of diluents

The extraction was carried out in different diluents such asoluene, xylene, benzene, dichloromethane and hexane from aque-us solution at pH 12 ± 0.1. Benzoic acid solubility in hexane wasoor. In toluene and xylene, high extraction percentages of dye werebtained compared to dichloromethane and benzene (Table 3). Suc-eeding tests were carried out using xylene as diluent since it is lessoxic compared to benzene and dichloromethane. About 99% of dyeas extracted into the solvent.

.4. Effect of dye concentration

The effect of initial dye concentration on the extraction processas tested at 2.9 × 10−2 M of benzoic acid in xylene. It can be seen

rom Fig. 4 that the percentage of dye extraction decreased withnitial dye concentration. At initial dye concentration of 50 mg/L,9% extraction was obtained. With further increase in dye concen-ration the percentage of extraction of dye decreased. However, thebsolute amount of dye extracted, increased with increase of initialye concentration.

.5. Effect of equilibration time

The amount of dye extracted into organic phase at differentimes (up to 15 min) was studied. Fig. 5 shows that at 3 min maxi-

um extraction was 95% at initial dye concentration of 50 mg/L. Thextraction efficiency of dye increased with increase in equilibra-ion time. Maximum extraction (99%) at initial dye concentrationf 50 mg/L was achieved at 10 min. After 10 min, almost all dye wasransported to the organic phase and hence an equilibrium periodf 10 min is recommended.

.6. Effect of temperature

Fig. 6 shows the effect of temperature on extraction of dye fromqueous phase. It can be seen that the extraction rate remainednchanged at 99% from 20 to 28 ◦C. When the temperature wasaised from 28 to 50 ◦C, the extraction rate decreased. So the effect

ig. 4. Effect of dye concentration (experimental conditions: volume of sourcehase = 25 mL at pH 12 ± 0.1, volume of organic phase = 25 mL, extractant concen-ration 2.9 × 10−2 M, equilibration time = 10 min).

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ig. 6. Effect of temperature (experimental conditions: volume of sourcehase = 25 mL at pH 12 ± 0.1, volume of organic phase = 25 mL, extractant concen-ration 2.9 × 10−2 M, equilibration time = 10 min).

f temperature on extraction was not very significant at room tem-erature. Further studies were carried out at 27 ◦C.

.7. Effect of extraction phase ratio

The phase volume ratios (aqueous to organic phase volume) of:1, 5:1, 10:5, 15:1 were used to study the effect of phase ratio onxtraction with initial dye concentration from 50 to 500 mg/L. Theesults are presented in Table 4. From Table 4 it is evident thator the ratio of 15:1 the removal efficiency dropped from 75 to3% when initial dye concentration changed from 50 to 500 mg/L.hen the ratio was reduced to 5:1 the removal efficiency changed

rom 92 to 81%. For the ratio of 1:1 the percentage of dye removal

hanged from 99 to 90%. The ratio 1:1 yielded high percentage ofye removal probably because the free concentration of benzoiccid in the organic phase is higher when the aqueous to organichase ratio (A/O) is lower.

able 4ffect of extraction phase ratio on percentage of dye extraction with initial dyeoncentration from 50 to 500 mg/L

atio (A/O) Extracted dye (mg/L) Percentage of dye extraction

50 100 200 300 500 50 100 200 300 500

1:1 49 96 190 282 450 99 96 95 94 905:1 46 90 176 258 405 92 90 88 86 817:1 43 85 166 240 360 87 85 83 80 75

10:1 40 77 150 216 340 80 77 75 72 6815:1 37 72 140 204 315 75 72 70 68 63

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G. Muthuraman et al. / Journal of Hazardous Materials 163 (2009) 363–369 367

Fig. 7. Effect of loading capacity of dye for benzoic acid (experimental conditions:vet

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Table 6Effect of stripping agents on percentage of dye stripping

Stripping agent Percentage of stripping

HCl (0.5N) 80.0HCl (1.0N) 80.0HNO3 (0.5N) 35.0HNO3 (1.0N) 35.0H2SO4 (0.5N) 90.0HH

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olume of source phase = 25 mL at pH 12 ± 0.1, volume of organic phase = 25 mL,xtractant concentration 2.9 × 10−2 M, dye concentration 50 mg/L, equilibrationime = 10 min).

.8. Loading of dye in benzoic acid

Benzoic acid (2.91 × 10−2 M) in 25 mL of xylene diluent was usedor extraction at ambient temperature of 27 ◦C for 15 min with equalolume of aqueous solution containing 50 mg/L of dye. The aqueoushase was analyzed for dye concentration after each stage of extrac-ion and cumulative dye content transferred into organic phase wasalculated. The plot of cumulative dye content per 2.91 × 10−2 Menzoic acid versus number of stages is depicted in Fig. 7. After fivetages, emulsion was noticed. This might be because the extrac-ant was unable to extract dye from the feed solution. It is clearrom Fig. 7 that the loading capacity of benzoic acid in xylene forxtraction of dye from aqueous solution was 9–9.5 mg of dye per.91 × 10−2 M of extractant.

.9. Effect of salt concentration

In the actual textile dye bath effluent the dye waste containsalts like sodium chloride and sodium sulphate. To understandhe influence of sulphate and chloride concentration on dyextraction, dye solutions with different concentrations of sodiumhloride and sodium sulphate were prepared and tested at pH2 ± 0.1. Table 5 shows the effect of sodium chloride and sodiumulphate on percentage removal of dye from aqueous solutionsn the presence of benzoic acid as an extractant and at pH2 ± 0.1. It can be seen that the percentage removal of dye was

ot affected with increase in sodium chloride and sodium sul-hate concentrations up to 5000 mg/L in the aqueous sourcehase.

able 5ffect of salt concentration on percentage of dye extraction with initial dye concen-ration from 50 to 500 mg/L

oncentration of anions (mg/L) Percentage of dye extraction

50 100 200 300 500

hloride1000 99.0 96.0 95.0 94.0 90.02000 99.0 95.9 95.0 94.1 90.13000 98.9 96.0 95.2 94.0 90.04000 99.0 96.0 94.0 94.0 90.15000 98.9 96.1 95.1 94.0 90.1

ulphate1000 99.0 95.8 95.0 94.0 90.02000 99.0 96.0 95.0 94.0 90.13000 98.0 96.0 94.7 94.0 90.14000 99.0 96.0 95.0 93.8 90.05000 99.0 96.0 95.0 94.0 90.0

i

3

u

Fpt

2SO4 (1.0N) 96.02SO4 (2.0N) 96.0

xtraction phase ratio 1:1.

.10. Effect of stripping reagents

In extraction processes, it is very imperative to back extract thextracted dye from the organic phase and allow recycling of therganic solvent without loss of efficiency. Various inorganic acidsuch as HCl, HNO3 and H2SO4 were used as stripping agent in thistudy. Sulphuric acid stripped the dye very well from the organichase (Table 6) compared to other inorganic acids. It means thathe presence of H2SO4 in the stripping phase helped the dye byonverting the dye hydrophilic moiety [30]. Hence 1N H2SO4 wasound to be suitable for stripping of the extracted dye. The max-mum amount of dye (96%) was stripped within 10 min. Furtherncrease in time did not improve stripping efficiency.

.11. Effect of stripping phase ratio

The stripping phase ratio (organic to aqueous) is an impor-ant factor in stripping process. From Fig. 8, the percentage ofye stripping increased with decreasing phase ratio (O/A). When/A = 1/1–2/1, at fixed 1N H2SO4, the stripping rates were higher

han 95%. However, when the ratio O/A was greater than 3/1, thefficiency of stripping decreased. This might be because the quan-ity of stripping reagent was not enough to neutralize the alkali inhe organic phase. Thus, a phase ratio O/A of 2/1 was maintained.

.12. Effect of stripping contact time

The stripping efficiency did not increase with increasing contactime in the range 3–10 min, when a freshly loaded organic solutionas used. This indicates the stripping was very fast and the strip-ing reaction was completed within 5 min and 96% of the dye wastripped from the loaded organic phase. When contact time wasncreased, no further stripping was achieved.

.13. Reusability of solvent

The stripped organic solvent was reused for MB dye extractionnder the optimized condition and the results are presented in

ig. 8. Effect of stripping phase ratio (experimental conditions: volume of sourcehase = 25 mL at pH 12 ± 0.1, volume of organic phase = 25 mL, extractant concentra-ion 2.9 × 10−2 M, dye concentration 50 mg/L, volume of stripping reagent 12.5 mL).

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368 G. Muthuraman et al. / Journal of Hazardo

Table 7Reusability of solvent

No. of stage 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

P

E

Tcitt

3

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vto

4

e

•

•

•

•

•

A

ercentage of dyeextraction

99 99 99 99 99 99 99 99 99 99 96 93 91 89 87

xtraction phase ratio 1:1.

able 7. The extraction efficiency of dye did not decrease up to 10ycles. After 10 cycles, it was found that 87% MB dye was extractednto the solvent. This might be due to loss of benzoic acid duringhe stripping of dye. When 0.35 × 10−2 M of benzoic acid was addedo the recycled organic solvent the extraction increased to 99%.

.14. Application of the developed LLE for textile wastewater

The developed liquid–liquid extraction system was tested forpplicability to the real textile wastewater from a local textilendustry. The wastewater was alkaline in nature (pH 12.5 ± 0.1).nder optimized condition (volume of source phase = 25 mL, dyeoncentration 60 mg/L, volume of organic phase = 25 mL, extractant

−2

oncentration = 2.9 × 10 M, equilibration time = 10 min, volumef stripping reagent = 12.5 mL, residual dye concentration in theource phase was 3 mg/L) the textile dye waste was extracted veryell and the extracted dye stripped into sulphuric acid solution. Itas noticed that the extraction and stripping were not affected by

tiM

Fig. 9. A proposed flow sheet for extraction and r

us Materials 163 (2009) 363–369

arious types of salts present in the textile wastewater. Based onhe above data, a proposed flow sheet for extraction and recoveryf dye from industrial wastewater is given in Fig. 9.

. Conclusions

The method presented offers a simple approach for selectivextraction of cationic dye for removal and recovery.

Benzoic acid in xylene is able to extract more than 99% of cationicdye from aqueous solution in a short time of 10 min.The extraction efficiency of dye was not affected in the presenceof salts like NaCl and Na2SO4.Stripping efficiency of dye reduced with organic to aqueous phaseratio.Stripping reaction was completed within 5 min and 96% of thedye was stripped from loaded organic phase.Solvent (benzoic acid + xylene) can be reused as many as 10 timeswithout loss of efficiency.

cknowledgement

One of the authors expresses his thanks for being given oppor-unity to do a post-doctorate research under the fellowship schemen the Division of Environmental Technology, Universiti Sains

alaysia.

ecovery of dye from industrial wastewater.

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G. Muthuraman et al. / Journal of H

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